This K23 application will prepare the candidate for an independent research career in the clinical epidemiology of late-life mental disorders. The focus of the research project is to determine the degree to which early and mid-life depressive spectrum disorder increases risk of developing cognitive deficits in later life. Late-life depression has been associated with subsequent development of cognitive deficits in late life,but no previous study has examined the association between early and mid-life depression and later life cognitive deficits. The proposed study provides an unusual, time-sensitive opportunity to test this hypothesis by taking advantage of the recently funded fourth wave of the Baltimore Epidemiologic Catchment Area (ECA) study. Using a retrospective cohort design, the investigator proposes to sample people with depression before age 50 as assessed in previous waves of the Baltimore ECA studies, and examine their neuropsychological outcomes 10 to 23 years later. The specific aims of the proposal are: 1) to determine whether early and mid-life depressive spectrum disorder (before age 50) increases risk of developing Mild Cognitive Impairment or dementia in later life (after age 60), 2) to investigate the longitudinal association between early and mid-life depressive spectrum disorder and late life cognitive deficits in specific neuropsychological domains (i.e. executive function and memory), and 3) to estimate what extent duration, number of episodes, and severity of early and mid-life depressive spectrum disorder predict cognitive impairment in late life. This study will serve as a vehicle for the candidate to obtain invaluable experience in the design and fieldwork of an epidemiologic study of the aging population. To complement his practical research training, the candidate will concurrently enroll in formal courses in Epidemiology and Biostatistics of Aging and fulfill the requirements for a Master's degree. He will participate in seminars in the post-doctoral program in neuropsychology to develop advanced knowledge in use and interpretation of neuropsychological instruments. A panel of mentors and consultants (Drs. Constantine Lyketsos, William Eaton, Jason Brandt, George Rebok, Kung-Yee Liang, George Alexopoulos, and Anand Kumar) will guide his research and training. This award will provide groundwork for his long term goal of becoming an expert in clinical epidemiology of late life mental disorders.